JP2017115764A - Controller of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance startability of an engine in a warm state of the engine.SOLUTION: A controller of an engine includes: a mechanical supercharger 10 including a mechanical compressor 11 arranged in a suction passage 4 and configured to supercharge suctioned air introduced into a combustion chamber, and an exhaust turbine 12 arranged in an exhaust passage 14; an exhaust bypass valve 42 configured to open/close an exhaust bypass passage 41 connecting an upstream side and a downstream side of the exhaust turbine 12 in the exhaust passage 14; an electric supercharger 30 including an electric compressor 32 arranged in the suction passage 4 and configured to supercharge suctioned air to the combustion chamber. The controller is configured to, in start of the engine, make the exhaust bypass valve 42 into an opened state and drive the electric supercharger 30 in a case where the engine is in a warm state, and make the exhaust bypass valve 42 into a closed state in a case where the engine is in a cold state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an engine control device including an electric supercharger that supercharges intake air with an electric motor and a mechanical supercharger that recovers energy of exhaust gas by a turbine and supercharges intake air.

  Engines equipped with a mechanical supercharger that supercharges intake air introduced into a combustion chamber using the energy of exhaust gas are widely adopted.

  This type of mechanical supercharger, also called a turbocharger, is configured by arranging a compressor in the middle of the intake passage of the engine, placing a turbine in the middle of the exhaust passage, and rotating the turbine with exhaust gas flowing through the exhaust passage. The compressor is operated to increase the amount of intake air into the combustion chamber to improve the engine torque.

  In recent years, various types of electric superchargers have been proposed in which a compressor is driven by an electric motor in addition to a supercharger using the energy of exhaust gas. The electric supercharger has an advantage that it can be supercharged arbitrarily by supplying electric power regardless of the operating state of the engine (see, for example, Patent Document 1).

  A mechanical supercharger that uses the energy of exhaust gas employs a waste gate valve that adjusts the amount of inflow into the turbine by diverting a part of the exhaust gas. The supercharging pressure of intake air can be controlled by adjusting the amount of exhaust gas passing through the turbine with a waste gate valve.

  Conventional waste gate valves have been controlled by pneumatic actuators using supercharging pressure as a power source, but in recent years, electrically controlled waste gate valves that are controlled to open and close by an electric motor have also been adopted. By making the waste gate valve electrically controlled, it can be driven even when the supercharging pressure is low, and more precise control is possible.

JP-A-2005-163694

  When the engine is in a warm state, for example, when the engine is stopped due to idling stop or the like, one of the cylinders corresponds to a valve overlap period in which the intake valve and the exhaust valve are simultaneously open. In the cylinder during the valve overlap period, the intake valve and the exhaust valve are open at the same time, so if the exhaust gas flows backward to the intake passage side and the engine is restarted in that state, the intake air required for combustion Oxygen may be insufficient. For this reason, there is a demand for removing exhaust gas that has flowed back and keeping the startability at a high temperature always high.

  SUMMARY OF THE INVENTION An object of the present invention is to improve engine startability in a warm state of the engine in which backflowed exhaust gas has a great influence on engine startability.

  In order to solve the above problems, the present invention provides a mechanical supercharger including a mechanical compressor that is disposed in an intake passage and supercharges intake air that is introduced into a combustion chamber, and an exhaust turbine that is disposed in an exhaust passage. An exhaust bypass valve that opens and closes an exhaust bypass passage connecting the upstream side and the downstream side of the exhaust turbine in the exhaust passage, and an electric compressor that is disposed in the intake passage and supercharges intake air to the combustion chamber And when the engine is warm, the exhaust bypass valve is opened, and when the engine is cold, the exhaust bypass valve is closed. The engine control system is used.

  Here, when the engine is in a warm state, it is desirable to drive the electric supercharger.

  An intake valve that opens and closes an opening of the intake passage to the combustion chamber; and an exhaust valve that opens and closes an opening of the exhaust passage to the combustion chamber. Both of the intake valve and the exhaust valve are opened. The effect of improving startability is particularly high when the valve overlap period is set.

  It is desirable that the electric supercharger is driven when the engine is in a warm state until the start of the engine is completed.

  Further, it is possible to adopt a configuration in which the exhaust bypass valve is kept open until the engine is completely started when the engine is in a warm state.

  According to the present invention, when starting the engine in the warm state, the exhaust bypass valve of the exhaust bypass passage that avoids the turbine of the mechanical supercharger in the exhaust passage is opened, so that the exhaust passage backflows from the exhaust passage to the intake passage. Exhaust gas can be efficiently discharged into the exhaust passage, and engine startability can be improved.

It is a schematic diagram of the control apparatus of the engine which shows embodiment of this invention. It is a graph which shows the time of starting of the engine of this invention. It is a flowchart which shows control of the engine of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view conceptually showing an engine control device E according to this embodiment.

  The engine 1 of this embodiment is a four-cycle gasoline engine for automobiles. As shown in FIG. 1, the configuration of the engine 1 includes an intake port 3 for sending intake air into a cylinder 2 having a combustion chamber therein, an intake passage 4 leading to the intake port 3, and an exhaust passage 14 drawn from the exhaust port 13. And a fuel injection device for injecting fuel into the intake port 3 or the combustion chamber. The intake port 3 and the exhaust port 13 are opened and closed by valves.

  In this embodiment, a four-cylinder engine having four cylinders is assumed, but the present invention can be applied regardless of the number of cylinders.

  In the intake passage 4 leading to the combustion chamber, a throttle valve 5 that adjusts a flow area to the intake port 3 toward the upstream side from the intake port 3 that is a connection portion to the combustion chamber, intake air flowing through the intake passage 4 An intake air cooling device (intercooler) 6 for cooling, a mechanical compressor 11 of a mechanical supercharger (turbocharger) 10, and a second throttle valve 7 for adjusting the flow area in the intake passage 4 on the upstream side, An air cleaner (not shown) or the like is provided.

  In the exhaust passage 14, the turbine 12 of the mechanical supercharger 10, a catalyst for removing unburned hydrocarbons (HC) and the like in the exhaust, etc. from the exhaust port 13, which is a connection portion to the combustion chamber, toward the downstream side. Are provided with an exhaust purification unit 15, a silencer 16, and the like.

  As shown in FIG. 1, the mechanical supercharger 10 includes a mechanical compressor 11 that is disposed in the intake passage 4 and supercharges intake air that is introduced into the combustion chamber, and an exhaust turbine 12 that is disposed in the exhaust passage 14. Composed. When the exhaust turbine 12 is rotated by the exhaust gas flowing through the exhaust passage 14, the rotation is transmitted to the mechanical compressor 11 in the intake passage 4. The intake air flowing through the intake passage 4 is supercharged by the rotation of the mechanical compressor 11.

  Further, an exhaust bypass device 40 including an exhaust bypass passage 41 that connects the upstream side and the downstream side of the exhaust turbine 12 in the exhaust passage 14, and an exhaust bypass valve 42 that opens and closes the exhaust bypass passage 41, a so-called waste gate valve. A device is provided. If the exhaust bypass valve 42 is opened, a part of the exhaust gas flowing to the exhaust turbine 12 side is diverted to the exhaust bypass passage 41 side, and the exhaust energy applied to the exhaust turbine 12 is reduced.

  In this embodiment, the exhaust bypass valve 42 is an electrically controlled waste gate valve that is controlled to open and close by an electric motor.

  Further, an electric supercharger 30 is disposed in the middle of the intake passage 4. The electric supercharger 30 includes an electric compressor 32 that is disposed in the intake passage 4 and supercharges intake air into the combustion chamber. When the electric compressor 32 is driven by supplying electric power, the intake air flowing in the intake passage 4 is supercharged.

  The intake passage 4 is provided with an intake bypass passage 33 that connects the upstream side and the downstream side of the electric compressor 32, and an intake bypass valve 34 that opens and closes the intake bypass passage 33.

  Driving power for the exhaust bypass valve 42, the intake bypass valve 34, the electric compressor 32, and the like is supplied from a battery 60. Here, the battery 60 that supplies power to the exhaust bypass valve 42, the intake bypass valve 34, the electric compressor 32, and the like is common to the battery that supplies power to other parts of the engine 1 and the vehicle in which the engine 1 is mounted. It is said. However, the battery that supplies driving power to the exhaust bypass valve 42 and the electric compressor 32 can be provided separately from the battery that supplies power to the engine 1 and the entire vehicle.

  A downstream side of the exhaust turbine 12 in the exhaust passage 14 and a midway portion between the mechanical compressor 11 and the second throttle valve 7 in the intake passage 11 are communicated by an exhaust gas recirculation passage 21 constituting the exhaust gas recirculation device 20. . A part of the exhaust gas discharged from the combustion chamber returns to the upstream side of the mechanical compressor 11 and the electric compressor 32 in the intake passage 4 as the recirculation gas via the exhaust recirculation passage 21. An exhaust gas recirculation valve 22 is provided in the exhaust gas recirculation passage 21. The recirculated gas merges with the intake air in the intake passage 4 in accordance with the pressure state in the intake passage 4 that accompanies the opening and closing of the exhaust gas recirculation valve 22 and the opening and closing of the second throttle valve 7.

  A vehicle equipped with the engine 1 includes an electronic control unit 50 for controlling the engine 1.

  The electronic control unit 50 controls fuel injection by a fuel injection device (not shown) provided in the intake port 3 or the combustion chamber, supercharging pressure control, opening control of the throttle valve 5 and the second throttle valve 7, exhaust gas Commands necessary for control of the gas recirculation device 20 and other control of the engine are performed.

  The electronic control unit 50 also controls the mechanical supercharger control means 51 for controlling the mechanical supercharger 10, the electric supercharger control means 52 for controlling the electric supercharger 30, and the intake bypass valve 34. And an exhaust bypass device control means 54 for controlling the exhaust bypass valve 42 of the exhaust bypass device 40.

  As shown in FIG. 1, the intake passage 4 is provided with a purge device a that temporarily stores the evaporated fuel generated in the fuel tank in a canister or the like and introduces it into the downstream side of the throttle valve 5. . Further, a blow-by gas recirculation device b that recirculates the blow-by gas mainly containing unburned gas leaked into the engine 1 to the intake port 3, opens to the upstream side of the second throttle valve 7, and the pressure in the crankcase A breather device e and the like are provided. These devices are also controlled by the electronic control unit 50.

  Further, in the intake passage 4, as a sensor device for acquiring information necessary for controlling the engine 1, a pressure sensor c on the downstream side of the throttle valve 5, a pressure sensor d on the upstream side of the throttle valve 5, and the inside of the intake passage 4 are provided. An air flow sensor f for detecting the amount of flowing air is provided.

  The exhaust passage 14 is provided with an exhaust temperature sensor g that detects the temperature of the exhaust gas as a sensor device that acquires information necessary for controlling the engine 1.

  Further, the engine 1 is provided with a water temperature sensor i for detecting the temperature of the cooling water for cooling the cylinder block and the like, and a rotation speed sensor j for detecting the rotation speed of the crankshaft of the engine 1. The vehicle is provided with an accelerator opening sensor k that detects the amount of depression of the accelerator.

  Information on these various sensors can be acquired by the electronic control unit 50 through a cable.

  Hereinafter, the control at the start of the engine 1 will be described based on the flowchart of FIG.

  First, in step S1, the driver makes a start request for the engine 1 with an ignition starter switch.

  In response to the starter switch ON operation signal, in step S2, the accelerator opening detected by the accelerator opening sensor k, the coolant temperature detected by the water temperature sensor i, and the like are read into the electronic control unit 50. .

  In step S3, when it is determined that the engine 1 is in a warm state, that is, when the coolant temperature is equal to or higher than a predetermined water temperature (for example, 60 ° C.) that is a reference value, the process proceeds to step S4 and the exhaust bypass is performed. Control for opening the exhaust bypass valve 42 of the device 40 is performed. As the start of the engine 1 in the warm state, for example, a situation of restart from an idling stop, a case where the vehicle is stopped and the engine is stopped, and then immediately restarted to start are considered.

  Further, when it is determined that the engine 1 is in a cold state at the time of start-up, that is, when the coolant temperature is lower than a predetermined water temperature (for example, 60 ° C.) that is a reference value, the process proceeds to step S5 and the exhaust gas is exhausted. Control for closing the exhaust bypass valve 42 of the bypass device 40 is performed.

  Subsequently, in step S6, the electric compressor 32 of the electric supercharger 30 is driven, and the supercharged intake air is introduced into the combustion chamber.

  In step S7, a starter switch ON operation signal is received, and the starter provided in the engine 1 is driven by electric power. When the starter is driven, the rotational speed of the crankshaft of the engine 1 is detected by the rotational speed sensor j. The rotational speed of the crankshaft is read into the electronic control unit 50.

Further, in the control of the engine 1, the valve over is in a state where both the intake valve that opens and closes the opening of the intake passage 4 to the combustion chamber and the exhaust valve that opens and closes the opening of the exhaust passage 14 to the combustion chamber are opened. A lap period is set.

  Since the exhaust bypass valve 42 is opened when the engine temperature is high, the influence of the back-flowing exhaust gas on the engine startability is suppressed, so that an increase in the pressure of the exhaust port 13 is suppressed. In any one of the cylinders 2 corresponding to the lap period, the exhaust gas flowing backward from the exhaust passage 14 toward the combustion chamber or the intake passage 4 can be quickly discharged toward the exhaust passage 14. For this reason, the intake air is smoothly introduced into the fuel chamber, and the startability of the engine 1 is improved. At this time, by driving the electric supercharger 30 together, the exhaust gas flowing backward to the combustion chamber or the intake passage 4 side can be discharged more rapidly toward the exhaust passage 14. For this reason, the startability in the warm state can be improved.

  On the other hand, since the exhaust bypass valve 42 is closed when the engine is cold, which has a large influence on engine startability due to a decrease in the cranking speed, the pressure increase in the exhaust port 13 is promoted. In any cylinder 2 corresponding to the valve overlap period, the so-called blow-through phenomenon in which the intake air introduced from the intake port 3 into the combustion chamber flows into the exhaust port 13 as it is can be suppressed. From this, sufficient intake air can be filled into the combustion chamber. For this reason, the startability of the engine 1 is improved. At this time, the charging of the intake air into the combustion chamber can be further increased by driving the electric supercharger 30 together. For this reason, the startability in the cold state can be improved.

  Here, it is desirable that driving of the electric supercharger 30 at the start of the engine 1 is performed at least until the start of the engine is completed in both the warm state and the cold state. In this embodiment, when the start of the engine is completed, the starter is stopped, and at the same time, the driving of the electric supercharger 30 is stopped to reduce the power consumption (see Step S8, Step S9, and Step S10). ).

  Whether or not the engine 1 has been started can be determined by the start determination means 55 provided in the electronic control unit 50 based on fluctuations in the rotational speed of the crankshaft of the engine 1. As shown by reference sign p1 in FIG. 2, when crankshaft rotation speed reaches the complete explosion speed during cranking by driving the starter, the completion of the start (complete explosion) is determined.

  In the period t1 in FIG. 2, the electric supercharger 30 is driven and the exhaust bypass valve 42 is maintained in the open state during the period from the ON operation of the ignition starter switch to the completion of the start in the warm state of this embodiment. Shows the period.

  However, as a modification of the control in the warm state, the period for driving the electric supercharger 30 and maintaining the open state of the exhaust bypass valve 42 is not limited to the period t1, for example, t1 and t2. You may set to the period which united. The period t2 is set up to the time when the overshoot of the rotational speed at the start ends.

  The open state of the exhaust bypass valve 42 at the start in the warm state is maintained at least until the start of the engine is completed, but is controlled so as to be open when the exhaust bypass valve 42 is closed. (Refer to step S11 and step S12). After the start of the engine is completed (see step S13), the exhaust bypass valve 42 is selected between an open state and a closed state by normal operation control.

  Further, a period t1 in FIG. 2 is a period for driving the electric supercharger 30 and maintaining the closed state of the exhaust bypass valve 42, which is performed from the ON operation of the ignition starter switch in the cold state to the completion of the start. It can also be.

  However, as a modified example of the control in the cold state, the period of driving the electric supercharger 30 and maintaining the closed state of the exhaust bypass valve 42 is not limited to the period of t1, for example, t1 and t2. It may be set to a combined period. The period t2 is set up to the time when the overshoot of the rotational speed at the start ends.

  The closed state of the exhaust bypass valve 42 at the start in the cold state is maintained at least until the start of the engine is completed, but the exhaust bypass valve 42 is opened after the start of the engine is completed. The switching of the exhaust bypass valve 42 from the closed state to the open state can be performed simultaneously with the stop of the drive of the electric supercharger 30 or after the stop of the drive. After the start of the engine is completed, exhaust pump loss and residual combustion gas can be reduced at an early stage by opening the exhaust bypass valve 42 and lowering the exhaust port pressure.

  At this time, the setting of the exhaust bypass valve 42 to the open state may be a period t4 in FIG. 2 in which the rotation of the engine 1 is stabilized and the temperature raising control of the exhaust purification unit 15 is started, or immediately before the overshoot before that. It is good also as a period which combined t3 and t4 including period t3. Further, when the driving of the electric supercharger 30 is finished in the period t1, the open state of the exhaust bypass valve 42 may be a period in which the periods t2, t3, and t4 are combined.

  In this embodiment, the exhaust bypass device 40, that is, the waste gate valve device is electrically controlled, so that it can be driven even when the supercharging pressure is low, and more precise control is possible. Although it may be controlled by a pneumatic actuator, the effect is reduced because the waste gate valve is operated after the pressure is generated. At this time, it is desirable to use a negative pressure type using a vacuum pump.

  In this embodiment, the temperature of the cooling water for cooling the cylinder block or the like of the engine 1 is used to determine whether the engine 1 is warm or cold. For example, you may use the temperature of the lubricating oil of the engine 1, the temperature of the member which comprises the cylinder block of the engine 1, etc.

  Although the engine 1 of this embodiment is a four-cycle gasoline engine for automobiles, the present invention is not limited to this embodiment, and the present invention can be applied to a diesel engine as well as other types of gasoline engines.

1 Engine 2 Cylinder 3 Intake port 4 Intake passage 5 Throttle valve 6 Intake cooling device (intercooler)
7 Second throttle valve 10 Mechanical supercharger 11 Mechanical compressor 12 Exhaust turbine 13 Exhaust port 14 Exhaust passage 15 Exhaust purifier 16 Silencer 20 Exhaust gas recirculation device 21 Low pressure exhaust gas recirculation passage 22 Exhaust gas recirculation valve 30 Electric supercharger 32 Electric compressor 33 Intake bypass passage 34 Intake bypass valve 40 Exhaust bypass device 41 Exhaust bypass passage 42 Exhaust bypass valve 50 Electronic control unit 51 Mechanical supercharger control means 52 Electric supercharger control means 53 Intake bypass device control means 54 Exhaust bypass device control means 55 Start determination means

Claims (5)

A mechanical supercharger including a mechanical compressor that is disposed in the intake passage and supercharges intake air that is introduced into the combustion chamber; and an exhaust turbine that is disposed in the exhaust passage;
An exhaust bypass valve for opening and closing an exhaust bypass passage connecting the upstream side and the downstream side of the exhaust turbine in the exhaust passage;
An electric supercharger provided with an electric compressor disposed in the intake passage for supercharging intake air to the combustion chamber;
With
An engine control device that, when the engine is started, opens the exhaust bypass valve when the engine is warm, and closes the exhaust bypass valve when the engine is cold. The engine control device according to claim 1, wherein when the engine is started, the electric supercharger is driven when the engine is in a warm state. An intake valve for opening and closing an opening of the intake passage to the combustion chamber;
An exhaust valve for opening and closing an opening of the exhaust passage to the combustion chamber;
With
The engine control device according to claim 2, wherein a valve overlap period in which both the intake valve and the exhaust valve are opened is set. The engine control device according to claim 2 or 3, wherein the driving of the electric supercharger when the engine is in a warm state is performed until the start of the engine is completed. The engine control device according to any one of claims 1 to 4, wherein an open state of the exhaust bypass valve when the engine is in a warm state is maintained until the start of the engine is completed.

Images